Impact of Nb2O5 on the Glass Structure and Quantum Efficiency of Eu3+–doped Phosphate Glasses

Abstract This work investigates the influence of Nb 2 O 5 incorporation on the structural and luminescent properties of Eu 3+ –doped phosphate glasses. Raman spectroscopy revealed that the addition of Nb 2 O 5 promotes the substitution of PO 4 units by NbO 6 octahedra, leading to depolymerization of the glass network and a reduction in phonon energy. Optical absorption spectra showed a redshift in the absorption edge and a decrease in the optical band gap, associated with an increased number of nonbonding oxygens. Photoluminescence spectra exhibited an enhancement in the hypersensitive 5 D 0 → 7 F 2 transition and increases in both the relative intensity ratio ( R ) and the Judd–Ofelt parameter Ω 2 , indicating a rise in local asymmetry. Lifetime measurements revealed a reduction in the experimental lifetime, along with an increase in total radiative emission rate and suppression of non–radiative processes, yielding a quantum efficiency of up to 93%. These findings demonstrate that Nb 2 O 5 incorporation significantly improves the red emission efficiency of Eu 3+ ions in phosphate glass matrices.